This invention relates in general to generating sounds electronically, and more particularly to generating sounds which simulate percussive sounds without using stored samples of the sounds sought to be so generated so as to substantially reduced the amount of memory needed to store parameters for generating such sounds.
There are a number of methods in present use for generating music and sound electronically. Perhaps the most prevalent method is that of the Musical Instrument Digital Interface or MIDI. In MIDI devices musical instruments and sounds are specified in MIDI files and are generated via a sound synthesizer. Wavetable Synthesis is one technique where the instrument or sound is recorded, and digitally sampled. These samples make up files known as wave table files. The wave table files are used to recreate the sound of a given musical instrument, or other sound. Typically, when sampling a harmonic or tonal instrument, such as a piano or horn, for example, the instrument is sampled at several different tonal pitches. When the MIDI device generates pitches that are between those sampled, the device interpolates between the stored samples to arrive at the desired pitch. The tonal and harmonic content, as well as the temporal aspects of the sound are inherent in the samples. These qualities distinguish one instrument from another, one sound from another. Because these qualities are inherent in the wavetable synthesizer file, there is no need to model them. Instead, when a particular instrument sound is to be played, the MIDI device only needs to know the desired pitch, and interpolate between two stored pitches if necessary.
Tonal instrument sounds can be synthesized by frequency modulation (FM) techniques, where a given instrument can be modeled by one or more FM equations. FM techniques provide a way to create a reasonable facsimile of the sound of a particular tonal or harmonic instrument. However, FM techniques do not provide an acceptable means of recreating non-harmonic instruments and sounds, such as drums, cymbals, and other percussive sounds and sound effects such as a hand clap. For these sounds, wave table synthesis has been considered the better way for sound recreation. A standard MIDI system describes harmonic as well as percussion instruments. Thus, in order to generate faithful reproduction of music having percussion instrument sounds, wave tables will typically be used.
While the method of reproducing the sound of an instrument from a wave table is simple, and provides a qualitatively accurate reproduction, it requires an amount of memory not easily afforded in some embedded devices. An example of such an embedded device would be a cellular radiotelephone. Such devices are primarily designed for purposes other than generating music. However, in some markets, and in the mobile communication device market in particular, sound and music playing capability is offered as a market differentiator. Music can be used to provide an alert when an incoming call is being received, for example. Some manufacturers have designed communication devices which permit the user of the device to program tone sequences representative of songs into the device. However, because of the amount of memory needed to reproduce percussion sounds, the musical ability of such devices has been limited. Therefore there is a need for method of generating percussive sounds that uses substantially less memory than wave table techniques.